Foreign ministers from the Arab League have decided to extend the 22-nation bloc's observer mission in Syria for an extra month.

League officials also said Sunday the number of observers will be increased and they will receive training by the United Nations.

The officials were speaking on condition of anonymity in Cairo on Sunday, where the Arab League has been meeting to review the mission's report after its month-long mandate expired last Thursday.

The 165 observers were overseeing a peace protocol the Syrian government agreed to in November.

The meeting in Cairo was taking place amid further reports of violence plaguing Syria.

Activists say army deserters, following fierce fighting with security forces, briefly took control of the Damascus suburb of Douma on Saturday, only to later retreat for fear the government would order reprisal raids.

According to activists and human rights groups, the incident in Douma, less than 15 kilometres north of Damascus, was triggered after security forces opened fire on a funeral, killing four people.

Armed rebels from the self-styled Free Syrian Army were then reported to have taken over the streets in some areas of the suburb, driving security forces out.

Residents reported hearing explosions and gunfire. But activists said the rebels later withdrew, for fear of provoking a major assault on the area by regime forces.

The head of the British-based Syrian Observatory for Human Rights, Rami Abdul-Rahman, said government troops have also since retreated from the streets.

He said as of early Sunday, government forces had pulled back to a provincial headquarters and a security agency building in the Damascus suburb. Abdul-Rahman had no information on casualties.

Elsewhere in northwestern Syria, at least 14 people were killed Saturday after a van carrying prisoners was destroyed in a bomb attack.

The state news agency SANA blamed the attack on "terrorists" and said it occurred on the Idlib-Ariha highway, an area near the Turkish border that has witnessed intense fighting with army defectors recently.

Four bombs that went off in "two phases" hit the truck, and then attackers targeted an ambulance that arrived to assist the wounded, SANA reported.

The United Nations estimates more than 5,000 people in violence related to the uprising that began last March against President Bashar al-Assad's regime. Syria has restricted the international media's entry and attempts to report from the country and only recently agreed to allow reporters in for a government-monitored tour.

With files from The Associated Press